This is one of those classic moment when "You know your addicted to RC when you go car shopping and and look for one that can haul the most/ biggest airplanes." of course its a little to late for that now.

One suggestion that comes to mind is this. What if you cut a heavy duty peice of plywood that you can use as a joiner that has the same angle of your dihedral and make it long enough so it can give good support for each wing. Then you can make like a plywood channel in each wing half where the "joiner" would slide into. Then for attaching it to the plane you probably would need one indexing pin on the leading edge of both wings to hold it down in the front, and for the back you would need to secure it with one screw on each wing half. Then of course, your wing struts would definatly half to be more so functional then just for decoration so you might half to re-engineer them now as well.

I dont know exactly how that cub is built or how the wing attaches so this suggestion may or may not work, It would be a little chore to undertake what I discribed but it would work. There are many ways it can be done, you just need to do a little creative engineering.